1. Field of the Invention
The present invention relates to a recording/reproduction apparatus and a recording/reproduction system, and more particularly to a recording/reproduction apparatus and a recording/reproduction system that use near-field light.
2. Description of the Related Art
In recent years, technologies in which near-field light is utilized as recording light to record information on information recording media at a high density have been proposed. In the case where near-field light is used, it is possible to form minute light spots that exceed the diffraction limit of light. For example, a heat-assisted magnetic recording technology that uses near-field light is receiving attention as a promising next-generation high-density magnetic recording technology. There are proposals for various applications of near-field light to information recording media that use magneto-optical recording films or phase-change recording films.
One method for producing near-field light uses a surface plasmon resonance phenomenon that occurs when a conductor is irradiated with light. In the method, for example, when a conductor that is in the shape of a rectangular parallelepiped and that is formed on a transparent substrate is irradiated with light, the polarization direction of which coincides with the longitudinal direction of the conductor, the electric field of the irradiation light causes polarization of charge in the conductor. Vibration of the polarized charge is called “surface plasmon”. When the resonant wavelength of the surface plasmon and the wavelength of the irradiation light match each other, resonance called “surface plasmon resonance” occurs. In this case, the conductor forms an electric dipole strongly polarized in its longitudinal direction. When the conductor forms an electric dipole, a large electromagnetic field is produced in the vicinity of both longitudinal ends of the conductor, which produces near-field light.
A technology for producing near-field light utilizing the surface plasmon resonance phenomenon of a conductor discussed above to record a servo signal using near-field light is proposed in the related art (see Japanese Unexamined Patent Application Publication No. 2007-334989 (JP-A-2007-334989), for example). FIG. 24 shows the configuration of a portion of a floating head proposed in JP-A-2007-334989 around a conductor. In a floating head 100 according to JP-A-2007-334989, a conductive layer 102 that produces a magnetic field is provided in a surface 101 opposing a magnetic disc, and the conductive layer 102 is reduced in width at a portion along the current application direction to form a pair of narrow portions 103.
According to JP-A-2007-334989, the pair of narrow portions 103 are irradiated with light with a current applied to the conductive layer 102 to produce a magnetic field. This causes the narrow portions 103 to produce near-field light so that a pair of servo signals are recorded at the pair of narrow portions 103 through the magnetic field and the near-field light. In the technology proposed in JP-A-2007-334989, as described above, a pair of servo signals are recorded using a narrow track width to achieve a high track pitch.